#define _GNU_SOURCE
#include <errno.h>
#include <sched.h>
#include "syscall.h"
#include "atomic.h"

#ifdef VDSO_GETCPU_SYM

static void *volatile vdso_func;

typedef long (*getcpu_f)(unsigned *, unsigned *, void *);

static long getcpu_init(unsigned *cpu, unsigned *node, void *unused)
{
    void *p = __vdsosym(VDSO_GETCPU_VER, VDSO_GETCPU_SYM);
    getcpu_f f = (getcpu_f)p;
    a_cas_p(&vdso_func, (void *)getcpu_init, p);
    return f ? f(cpu, node, unused) : -ENOSYS;
}

static void *volatile vdso_func = (void *)getcpu_init;

#endif

int sched_getcpu(void)
{
    int r;
    unsigned cpu;

#ifdef VDSO_GETCPU_SYM
    getcpu_f f = (getcpu_f)vdso_func;
    if (f) {
        r = f(&cpu, 0, 0);
        if (!r) return cpu;
        if (r != -ENOSYS) return __syscall_ret(r);
    }
#endif

    r = __syscall(SYS_getcpu, &cpu, 0, 0);
    if (!r) return cpu;
    return __syscall_ret(r);
}
